Late Quaternary carbonate sedimentation at the Sierra Leone Rise (eastern equatorial Atlantic Ocean)

In the eastern equatorial Atlantic Ocean, changes in the concentration of carbonate in Late Quaternary sediments resulted from reduced production of carbonate in surface waters and increased dilution with non-carbonate sediments during glacial maxima. During glacial stages, production of carbonate in surface water (measured as its accumulation rate in shallow, undissolved cores) decreased by one half. The glacial accumulation rate of non-carbonate components increased 1.5 to 4 times over Holocene values; the greatest increases occurred in the deepest cores.

Carbonate dissolution during stages 2, 3 and 4 increased the proportion of foraminiferal fragments and decreased the accumulation rate of susceptible species in the deep sites. In shallow sites, slightly increased dissolution can be detected during stage 3 while greatly increased dissolution occurred during stage 4. Bathymetric profiles of foraminiferal fragmentation and accumulation document a shoaling of the foraminiferal lysocline by 1000 m during glacial isotopic stages. We present a mass balance model of sediment accumulation for carbonate and insoluble components and from this model we estimate the rate of downslope transport and dissolution of carbonate at the Sierra Leone Rise. Our results show that during stage 4 the rate of carbonate loss to dissolution was greater than the rate observed today or during other interglacial stages. The calculated rates of dissolution for stages 2 and 3 are not significantly different from those calculated for stage 1.     

俄罗斯北极海(喀拉海)的生物地球化学

据1995—2003年SIRRO计划的研究成果,喀拉海是研究河流—海洋体系相互作用过程独一无二的地区。巨大的西伯利亚叶尼塞河和鄂毕河注入这个浅海。1995—2003年科学研究船“鲍利斯.彼得罗夫”号对喀拉海进行了国际性考察。提供的工作成果总结了俄罗斯科学院地球化学与分析化学研究所完成的研究成果。对整个海区200多个测站研究了沉积物的水化学参数,有机碳和碳酸盐碳的含量及同位素成分,水中浮游生物和悬浮物质以及烃类和溶解CO2。在大西洋水进入喀拉海区δ13C有机的变化范围为-22‰~-24‰,而在东北海区叶尼塞和鄂毕河口区则为-27‰~-30‰…     

北冰洋门捷列夫海岭富锰棕色层稀土元素组成特征与来源初步分析

北冰洋深海广泛分布的富锰棕色沉积层(棕色层)是海冰、洋流、物源供给等多种因素共同作用的结果,本文基于西北冰洋门捷列夫海岭ARC07-E25岩芯沉积物稀土元素与微量元素含量、颜色反射率参数、粗颗粒组分和无机碳含量的变化特征,对该类沉积层中稀土元素的组成特征、形成机制和物质来源进行了综合分析。结果显示,沉积物稀土元素总含量(∑REE)在122.37×10⁻⁶～231.94×10⁻⁶之间变化,北美页岩标准化配分模式显示出轻微的中稀土(MREE)富集以及由La、Ce、Nd主导的较强的轻稀土(LREE)优势。沉积物中∑REE随着粗组分颗粒(如冰筏碎屑)的增多而呈现降低趋势,表明门捷列夫海脊沉积物中的稀土元素主要富集在细粒沉积物中。根据∑REE在沉积物中的变化特征将E25岩芯沉积物划分为4种地层,反映出了冰期/间冰期的气候转变过程中温暖条件下形成的棕色层与寒冷条件下形成的浅灰绿色沉积层(灰色层)的岩性旋回中稀土元素组成的差异,由于两种沉积层在形成时受到不同的底层水氧化还原环境的控制,导致了铈(Ce)元素在氧化水体中会由Ce³⁺氧化为Ce⁴⁺并发生沉降,而在还原水体中则由Ce⁴⁺还原为Ce³⁺发生溶解,这一特性使LREE含量产生较大波动,进而影响到∑REE,使之趋于在代表氧化条件的棕色层中升高而在代表还原条件的灰色层中降低。R型因子分析和物质来源判别结果显示,E25岩芯沉积物中稀土元素与亲碎屑元素(Nb、U、Th)有较好的相关性,主要来源于东西伯利亚海和新西伯利亚群岛的近岸侵蚀物质以及勒拿河物质的输入。     

Ocean bottom seismometer detection of earthquakes on the Gorda Rise near 41.5° north

The spatial and temporal distribution of microearthquake activity associated with the southern section of the Gorda Rise was monitored during a three week period using an array of four ocean bottom seismometers (OBS's) located at 41.5° N, 127.5° W on the rise axis. Sixty-two events were detected, of which roughly half occurred during a seismic swarm following an event of magnitude 4.9 that was well-recorded on land. A total of eighteen earthquakes could be located, seventeen of which originated from the valley floor, walls, and crestal mountains while the remaining event was located to the east of the rise in the Gorda plate. Well-constrained focal depths for four earthquakes ranged from roughly 4 to 12 km. Depths in excess of 10 km for two of the events provide strong evidence for the absence of a shallow steady-state magma chamber beneath the slow-spreading portion of the Gorda rise. Most of the events are believed to be the result of uplift of the crustal blocks comprising the valley walls. Four events located at an offset of the rise near 41.5° N may be related to strike-slip movement on a developing transform fault. Two of the events that occurred during the survey were large enough to be detected and located by land-based instruments. Comparison of these locations with the OBS locations indicates that well-recorded events having magnitudes of at least 4.5 are routinely mislocated 40–50 km to the east of their actual locations in this area while lower magnitude, poorly recorded earthquakes may have significantly larger location errors.     

Weak constraint data assimilation for tides in the Arctic Ocean

Estimation of the open-boundary inputs solving a weak constraint variational formulation for an Arctic tide model is considered as an ill-posed problem in the sense that the solution is very sensitive to the data noise and to grid size. Mathematically, spatial discretization of a cost function to be minimized and penalization of normal flow through the open boundary act as regularization of the problem. An heuristic choosing rule for the regularization parameter is applied to assess a suitable spatial resolution and the weight referred to the open boundary penalty. It is shown that these provide a better fit of the solution to a control data set compared with a finer grid, the value of the energy flux through the open boundary being in agreement with other model estimates. The M₂ solution obtained is much closer to the control data than other modern solutions while the accuracy of the simulated K₁ constituent is within the same error level. The tidal maps for these waves exhibit certain distinctions in comparison with other charts.     

Exploring the Arctic Ocean under Arctic amplification

正Rate of surface air temperature increase in the Arctic is roughly twice that of the global average, and this phenomenon is referred to as "Arctic Amplification"(Serreze and Barry, 2011). The Arctic sea ice season (October to September) of 2017–2018 is the second warmest in Arctic since 1900 (Overland et al., 2018); 2014–2018 are the five warmest years in the Arctic since 1900 (Overland et al.,2018). Mean temperatures in Finland, Norway, and Svalbard in May 2018 are the highest in the instrumental record since the early1900s (NOAA, 2018), and the extensive warm spells over Scandinavia led to extensive forest fires (Overland et al., 2018).     

Circulation patterns in the lower Arctic Ocean derived from geochemical data

Climatological water-mass structures were identified in the Arctic Ocean using the geochemical dataset in the Hydrochemical Atlas of the Arctic Ocean (HAAC) as well as data on a geochemically conserved parameter, PO₄*, based on phosphate and dissolved oxygen. In the upper ocean above a depth of 500 m, the HAAC was found to reliably depict the boundary between Pacific-Origin Water (P-Water) and Atlantic-Origin Water (A-Water), which is aligned 135°E–45°W near the surface but rotates counterclockwise with depth. Thus, the Arctic and Atlantic oceans exchange high-silicate P-Water and low-silicate A-Water. The PO₄* field in the lower ocean below a depth of 1500 m was analyzed statistically, and the results indicated that the Eurasian Basin receives low-PO₄* Nordic Seas Deep Water, which flows along the bottom from the Greenland Sea. The routes from the upper ocean to the lower ocean were determined. Only the southern portion of the Canada Basin, which receives water from the Chukchi and Beaufort Seas, has high PO₄* levels; the rest of the Amerasian Basin receives low-PO₄* water from the Laptev Sea and/or the Barents Sea. The Eurasian Basin receives moderate levels of PO₄* from the Fram Strait and from the intermediate layer. The intermediate-layer water gradually travels up from the lower ocean and returns to the Atlantic, entraining the subsurface portion. It is likely that high-PO₄* water occasionally flows down from the upper ocean along Greenland, making the Eurasian Basin heterogeneous.     

北极河流径流对北冰洋环流的影响

北极河流径流是北冰洋淡水的最大来源,其变化会对北冰洋中的诸多过程有重要影响。本文基于全球高分辨率海洋-海冰耦合模式的模拟结果,研究北冰洋温盐、海冰以及环流对北极河流径流的敏感性。通过对比有气候态北极河流径流输入的控制实验结果和径流完全关闭的敏感性实验结果,研究发现北极径流对北冰洋温度、盐度、海冰以及海洋环流等有显著的影响。关闭北极河流径流后,在河口附近的陆架上温度降低、盐度升高,且导致500 m深度处温度下降以及盐度升高;河口附近的陆架处,海冰密集度与海冰厚度增加。关闭北极河流径流也对北冰洋内的环流有影响:由于缺少来自欧亚大陆的北极径流的输入,穿极漂流与东格陵兰流流速减小且盐度增加;关闭北极径流导致近岸海表面高度降低,沿欧亚陆架的北冰洋边界流减弱,白令海入流增强。通过对比关闭北极径流实验与控制实验的温度和盐度剖面,发现关闭北极径流后大西洋层温度降低,各陆架海盐跃层的梯度减小,盐跃层厚度减小。     

北冰洋底发现火山

20 0 1年初 ,在北冰洋高纬度区进行海底测量的美国潜水调查船“Hawkhill”号上工作的科学家们发现了两座以前未知的活火山。在北地群岛 ( 86°N ,85°E)以北 ,利用声纳发现了两个不规则状尖顶隆起 ,其高度分别约为 50 0和1 0 0 0m。这些海山位于延伸 1km以上的加克利海岭的东部 ,该海岭分隔了南森和阿蒙森海盆。声波的高反射率说明隆起的顶部是光秃的 ,几乎未被新鲜的沉积物覆盖 ,它们是由年轻的玄武岩组成的。以夏威夷地球物理和行星学研究所MHEdwards为首的美国地球物理学家小组根据这一事实及在该区发现的特征性线性磁异常得出结论 :…     

北冰洋浮冰区湍流通量观测试验及参数化研究

利用2008年8月21～29日我国第3次北极考察期间在北冰洋海区(84°27′N,143°37′W～85°13′N,147°20′W)冰站观测的湍流资料及相关资料,对海冰近地层湍流通量及其特征参数进行了研究.结果表明:观测期间浮冰近地层始终存在逆温和逆湿层.这与我们以前(1999年在75°N和2003年在78°N)的观...     

Rotation of the Semail ophiolite (Oman): Additional Paleomagnetic data from the volcanic sequence

Thirty-two flows (247 cores) were sampled in the V1 (Geotimes) and V2 (Lasail) volcanic units of the Semail ophiolite, Oman (Aswad, Fizh, Hilti, Sarami, Wuqbah, and Tayin massifs). Paleomagnetic analysis of the samples was complicated by a large overlap of the two components of magnetization carried by the rocks: a crystalline remanent magnetization (CRM) acquired in the present day field, probably during weathering, and an older CRM probably produced by oxidation of the original titanomagnetites during hydrothermal event(s). If the magnetization carried by the V1 samples was acquired during the hydrothermal event related to the emplacement of these lava, e.g., during and/or shortly after cooling, the tectonic unity of the northern domain has to be questioned and a differential rotation considered between the Aswad and Hilti-Sarami massifs but, by the time of emplacement of the V2 series, this northern area seems to behave as one large unit. As only one set of data is available for the southern Tayin-Sumail massif, it is premature but a possible relative rotation on the order of 90° can be suspected between the Hilti-Sarami and Tayin-Sumail massifs, rotation which would have occurred after emplacement of the V2 series.     

基于观测数据的2003?2014年北冰洋海平面时空特征

本文对比了3个不同机构提供的北冰洋月均高度计数据,发现英国极地观测与建模中心和丹麦科技大学空间中心两套数据比较一致且空间覆盖率高,适用于北冰洋海平面变化研究,而前者在数据分辨率、平滑性和与验潮站的符合程度方面均更优。对高度计和验潮站数据的分析表明,北冰洋海平面的气候态特征表现为加拿大海盆的高值和欧亚海盆的低值之间形成鲜明对比;海平面的变化以季节变化和北极涛动引起的低频变化为主,加拿大海盆的季节和年际振幅均较大,俄罗斯沿岸海平面季节变化显著。2003?2014年,北冰洋平均海平面呈上升趋势,其中加拿大海盆海平面上升最快,而俄罗斯沿岸海平面有微弱下降趋势。加拿大海盆和俄罗斯沿岸由于海冰变化显著,不同高度计产品以及高度计与验潮站数据之间差别较大,使用时需慎重。     

试论海洋与中国的“和平崛起”

面对西方反华势力对“中国威胁论”的大肆渲染,中国政府提出了“和平崛起”的发展战略。在21世纪这个海洋世纪里,开发海洋的战略决策早已在中国政治经济及社会各界产生影响并得到初步实施。中国的“和平崛起”与海洋之间存在必然联系。文章从历史、地缘政治、经济等角度尝试分析海洋与中国“和平崛起”的关系。认为“和平崛起”的发展战略有着深厚的海洋文明的积淀;未来可能愈加尖锐的海洋权益之争是对中国“和平崛起”的挑战,也是中国表现其作为正义和平力量,热爱和平、要和平崛起的决心的机会;海洋经济对经济外交这一实现“和平崛起”的重要途径将会发挥重要作用。     

Hemipelagic deposits on the Mendeleev and northwestern Alpha submarine Ridges in the Arctic Ocean: acoustic stratigraphy,depositional environment and an inter-ridge correlation calibrated by the ACEX results

The first high resolution multichannel seismic data from the Mendeleev and Alpha Ridges in the Arctic Ocean have been used to investigate the depositional history, and compare acoustic stratigraphies of the three main sub-marine ridges (Mendeleev, Alpha and Lomonosov) in the polar ocean. Acoustic basement on the Mendeleev Ridge is covered by a ~0.6–0.8 s thick sediment drape over highs and up to 1.8 s within grabens. A pronounced angular discordance at 0.18–0.23 s below the seafloor along the middle to upper slopes divides the succession into an upper, undisturbed, uniformly thick, hemipelagic drape (Unit M1) and a partially truncated lower unit (Unit M2) characterized by strong reflection bands. Unit M2 is thicker in intra-ridge grabens and includes three sub-units with abundant debris flows in the uppermost subunit (M2a). The discordance between Units M1 and M2 most likely relates to instability along the middle to upper slopes and mass wasting, triggered by tectonic activity. The scars were further smoothed by bottom current erosion. We observe comparable acoustic stratigraphy and discordant relationships on the investigated northwestern part of Alpha Ridge. Similarly, on the central Lomonosov Ridge, Paleocene and younger sediments sampled by scientific drilling include an uppermost ~0.2 s thick drape overlying, highly reflective deposits with an angular unconformity confined to the upper slope on both sides of the ridge. Sediment instability on the three main ridges was most likely generated by a brief phase of tectonic activity (~14.5–22 Ma), coinciding with enhanced bottom circulation. These events are coeval with the initial opening of the Fram Strait. The age of the oldest sediments above acoustic basement on the Mendeleev- and west-central Alpha Ridges is estimated to be 70–75 Ma.     

Paleomagnetic results from deep-sea sediment of the Korea Deep Ocean Study (KODOS) area (northern equatorial Pacific) and their paleodepositional implications

Paleomagnetic properties of sediment cores were examined to reconstruct paleodepositional conditions in the Korea Deep Ocean Study (KODOS) area, located in the northeastern equatorial Pacific. The studied KODOS sediments have a stable remanent magnetization with both normal and reversed polarities, which are well correlated with the geomagnetic polarity timescale for the late Pliocene and Pleistocene. Average sedimentation rates are 1.56 and 0.88 mm/kiloyear for the Pleistocene and late Pliocene, respectively. Clay mineralogy and scanning electron microscope analyses of the sediments indicate that terrestrial material was transported to the deep-sea floor during these times. The variations of sedimentation rates with age may be explained by the onset of the northern hemisphere glaciation and subsequent climatic deterioration during the Pliocene and Pleistocene. For the Pleistocene, an increasing sedimentation rate implies that input of terrestrial materials was high, and also a high input of biogenic materials was detected as a result of increased primary production in the surface water. The down-core variations in paleomagnetic and rock-magnetic properties of the KODOS sediments were affected by dissolution processes in an oxic depositional regime. As shown by magnetic intensity and hysteresis parameters, the high natural remanent magnetization (NRM) stability in the upper, yellowish brown layers indicates that the magnetic carrier was in pseudo-single domain states. In the lower, dark brown sediments, only coarse magnetic grains survived dissolution and the NRM was carried by more abundant, multi-domain grains of low magnetic stability. The down-core variation of magnetic properties suggests that the KODOS sediments were subjected to dissolution processes resulting in a loss of the more stable components of the magnetic fraction with increasing core depth.     

北冰洋加克利海岭(AMORE-2001)的考察

20 0 1年 1 0月 7日俄罗斯极地与海洋研究所使用的德国科学研究船队的主要船只“Po larstern”号破冰船回到了德国不来梅港 ,结束了为期 1 0个星期的北冰洋中部的加克利海岭AMORE -2 0 0 1考察。“Polarstern”号上有由俄罗斯极地与海洋研究所所长ЙОРНТиде领导的来自德国、俄罗斯和美国的 60位科学家。另一艘美国“Healy”号海岸保护破冰船上有以塔尔萨大学PMichael教授为首的 2 0位美国科学家。2 0 0 1年 7月 3 1日晚两条破冰船从挪威的特罗姆瑟港出发 ,驶向欧亚深水盆地中部 ,去研究实际上不为人知的全世界洋中脊体系最北的地…     

Deep-water foraminifera communities of the Arctic Ocean

Sixteen foraminifera communities were distinguished on the basis of the quantitative analysis of the composition of the benthic foraminifera in the bottom sediments sampled at 254 stations at depths from 200 to 4411 m in the Arctic Ocean. The distribution of these communities is controlled by the environmental factors, which depend on the latitude and bathymetric zones of the Arctic Ocean, the currents, the water masses, and the content of calcium carbonate and organic carbon in the bottom water and in the sediments.     

基于中国北极考察布放浮标观测和数值模拟的海冰和积雪厚度变化分析

Sea ice and the snow pack on top of it were investigated using Chinese National Arctic Research Expedition(CHINARE) buoy data.Two polar hydrometeorological drifters,known as Zeno? ice stations,were deployed during CHINARE 2003.A new type of high-resolution Snow and Ice Mass Balance Arrays,known as SIMBA buoys,were deployed during CHINARE 2014.Data from those buoys were applied to investigate the thickness of sea ice and snow in the CHINARE domain.A simple approach was applied to estimate the average snow thickness on the basis of Zeno~ temperature data.Snow and ice thicknesses were also derived from vertical temperature profile data based on the SIMBA buoys.A one-dimensional snow and ice thermodynamic model(HIGHTSI) was applied to calculate the snow and ice thickness along the buoy drift trajectories.The model forcing was based on forecasts and analyses of the European Centre for Medium-Range Weather Forecasts(ECMWF).The Zeno~ buoys drifted in a confined area during 2003–2004.The snow thickness modelled applying HIGHTSI was consistent with results based on Zeno~ buoy data.The SIMBA buoys drifted from 81.1°N,157.4°W to 73.5°N,134.9°W in 15 months during2014–2015.The total ice thickness increased from an initial August 2014 value of 1.97 m to a maximum value of2.45 m before the onset of snow melt in May 2015;the last observation was approximately 1 m in late November2015.The ice thickness based on HIGHTSI agreed with SIMBA measurements,in particular when the seasonal variation of oceanic heat flux was taken into account,but the modelled snow thickness differed from the observed one.Sea ice thickness derived from SIMBA data was reasonably good in cold conditions,but challenges remain in both snow and ice thickness in summer.     

Mesozooplankton in the Arctic Ocean in summer

The biomass, species and chemical composition of the mesozooplankton and their impact on lower food levels were estimated along a transect across the Arctic Ocean. Mesozooplankton biomass in the upper 200 m of the water column was significantly higher (19–42 mg DW m^-3) than has previously been reported for the Arctic Ocean, and it reached a maximum at ca. 87°N in the Amundsen Basin. The lowest values were recorded in the Chukchi Sea and Nansen Basin, where ice cover was lower (50–80%) than in the central Arctic Ocean. In the deeper strata (200–500 m) of the Canadian and Eurasian Basins, the biomass was always much lower (4.35–16.44 mg DW m^-3). The C/N (g/g) ratio for the mesozooplankton population was high (6.5–8.5) but within the documented range. These high values (when compared to 4.5 at lower latitudes) may be explained by the high lipid content. Mesozooplankton accounted for approximately 40% of the total particulate organic carbon in the upper 100 m of the water column. Mesozooplankton species composition was homogeneous along the transect, consisting mainly of copepods (70–90% of the total number). It was dominated by four large copepod species (Calanus hyperboreus, C. glacialis, C. finmarchicus and Metridia longa), which together accounted for more than 80% of the total biomass. According to measurements of gut pigment and gut turnover rates, the mesozooplankton on average ingested between 6 and 30% of their body carbon per day as phytoplankton. Microzooplankton may have provided an additional source of energy for the mesozooplankton community. These data emphasize the importance of mesozooplankton in the arctic food web and reinforce the idea that the Arctic Ocean should no longer be considered to be a “biological desert”.